The invention relates to a plasma display panel comprising discharge spaces with a gas discharge mixture between a first substrate provided with display electrodes and a second substrate provided with projecting parts which define the discharge spaces, and provided with addressing electrodes and a fluorescent material.
Dependent on the type of display device, the fluorescent material is patterned or not patterned.
A display device of this type is used, inter alia, in large flat-panel display screens, for example, for HDTV.
A plasma display panel (PDP) of the type mentioned above is described in EP-A-0 779 643. This document describes measures for enhancing the luminance of such a panel. To this end, inter alia, a favorable composition of the gas discharge mixture (between 10% and less than 100% xenon) is proposed. A higher percentage of xenon is assumed to increase the quantity of UV radiation so that the number of photons incident on the fluorescent material for converting UV radiation to visible light in the fluorescent material is increased. However, it has been found that, at higher xenon percentages, the drive voltages, notably the minimal sustain and firing voltages are increased considerably.
It is an object of the present invention to obviate said increase of the drive voltages as much as possible.
To this end, a plasma display panel according to the invention is characterized in that a dielectric layer is present on the second substrate between the second substrate and the fluorescent material. For the dielectric layer, it preferably holds that the material of the dielectric layer has a dielectric constant of at least 7. The layer may be composed of a plurality of sub-layers. The relative dielectric constant is understood to be the value applying as a relative dielectric constant for computing the capacitance of a flat capacitor, of which said layer forms the dielectric.
It has been found that this leads to a decrease of said voltages, notably at higher percentages of xenon or another suitable gas (higher gas pressures). A possible explanation is the influence of the dielectric layer on the electric field, where also the curvature of the channel possibly plays a role when it is provided, for example, in a glass substrate by means of powder spraying.
The dielectric layer preferably comprises a material of the group of aluminum oxide (∈r=8), titanium oxide (∈r=14-100), tantalum oxide (∈r=20-42), thallium oxide, barium titanate, calcium titanate, strontium titanate, magnesium titanate, lead titanate and lead zirconate (for the titanates, ∈r is between 15 and 12,000). These materials have a high relative dielectric constant and can be provided in a simple manner, for example, by means of silk screening in relatively thick layers (5-30 xcexcm).
A preferred embodiment of a plasma display panel according to the invention is characterized in that the dielectric layer completely covers the walls of the discharge spaces. A maximum voltage decrease is thereby obtained.
A further preferred embodiment of a plasma display panel according to the invention is characterized in that the dielectric layer completely covers the addressing electrode, at least within a display element. This prevents the occurrence of unwanted spark discharges across the surface of the layer.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.